The present invention relates to a closed type compressor for use in refrigeration and, more particularly, to a closed type compressor which has an improved frame for retaining a compression means and an electric motor means in place.
A closed type compressor is constructed such that a compression means comprised of a cylinder and piston and an electric motor means comprised of a rotor and stator are provided within a case, whereby the piston of the compression means is driven by a crank shaft attached to the rotor so as to compress a cooling medium within the cylinder.
The compression means and electric motor means are mounted on a frame located within the case, said frame being retained in place within the case by means of, for example, a supporting member. This frame is the most basic element of all constituent elements of the compressor, and all of the other constituent elements are mounted with that frame used as a mounting base. For this reason, the method of mounting the frame is required to enable a high precision mounting of the frame in order to precisely locate the respective mounting positions for the compression means and motor means. Besides, the frame is also required to have a sufficient rigidity for supporting the compression means and motor means.
Conventionally, said frame is made principally of cast iron or the like and its rigidity is maintained by casting while, on the other hand, its precision is maintained by mechanical fabrication. However, where said frame is formed by casting, it becomes mechanically sound but fragile. As a result, the thickness of the resultant frame becomes large and the shape thereof also becomes large. Further, since the frame is mechanically fabricated after it has been cast, the fabrication cost becomes high.
Recently the demand is for a closed type compressor small in size, light in weight and low in cost, and, from this point of view as well, it is not preferable that the frame be formed by a casting. For this reason, a method of making the frame by plastic formation has been proposed. However, since such plastic formation is effected mainly by bending and drawing, it is difficult to maintain the precisions involved (particularly, flat plane, parallelism, dimension). Besides, it is impossible to obtain a frame having a sufficiently high rigidity, and it is virtually impossible to make the frame in the form of an integral unit by said plastic formation.